The use of resinous organic polymers to fabricate enclosure members (plastic containers) such as bottles, tanks and other containers and other molded articles is well known. Plastic containers which are made from most organic polymers, particularly the dominantly hydrocarbon polymers, are non-electroconductive, are non-adherent to polar materials such as inks, paints, dyes and various polar adhesives and are readily permeated and/or stress cracked or swollen by oleophilic materials such as liquid and gaseous hydrocarbons e.g., solvents, fumes, vapors, benzene, cyclohexane, xylene, chlorinated solvents, and hexane; gasses such as nitrogen, oxygen, helium, hydrogen, carbon dioxide, methane, ethane, propane, butane, freons; fuels such as gasoline, kerosene, fuel oils; oils such as natural fatty oils, lubricating oils, perfumes and agriculural chemicals. Depending on the particular polymer, these materials can adversely affect the container material. For example, natural fatty oils tend to cause stress cracking of polymers formed from olefinic monomers such as polyethylene. As a result of these inherent deficiencies many of such organic polymers must be treated with various agents which impart varying degrees of electroconductivity, adhesion and impermeability. Sulfonation techniques have been developed as one means of treating these polymeric materials to decrease the permeability and protect the polymeric material. Some of these sulfonation techniques are described in the following patents: U.S. Pat. Nos. 2,400,720; 2,937,066; 2,786,780; 2,832,696; 3,613,957 3.740,258; 3,770,706 and 4,220,739. In U.S. Pat. No. 4,220,739 the sulfonation technique is improved by employing as the sulfonating agent a gaseous mixture comprising sulfur trioxide and a suitably active halogen e.g. chlorine. The teachings of these patents are specifically incorporated herein by reference.
All of these prior sulfonation techniques require the generation of a suitable gaseous sulfonating agent such as, for example, sulfur trioxide. Also, in many of these processes, the sulfur trioxide treated organic resinous container is post-treated with a material which improves the effectiveness of the sulfonation treatment. Neutralization with ammonium, metal ions, as well as epoxidation of the organic polvmers employing a suitable organic epoxide have been utilized. These neutralization techniques also many times require the generation of gases.
In those processes employing gaseous treating agents, for example, sulfur trioxide, sulfur trioxide, ammonia, etc., gas generating equipment has been employed to generate mixtures of air and sulfur trioxide or neutralizing agents at the site where sulfonation is to be carried out. In many instances this gas generating equipment requires a capital investment which is as great as all the other equipment required to carry out the sulfonation process. Moreover, this equipment takes up considerable space and requires expert maintenance. Use of such equipment also requires start-up and shut-down procedures.
It would therefore be an improvement in the art-recognized processes of employing gaseous sulfonating compounds to treat the interior of resinous containers if a different method of generating the sulfonating and/or neutralizing gas could be employed. The present invention concerns such an improved method of sulfonating and/or neutralizing the interior surfaces of plastic containers which are made from resinous organic polymers which are capable of being surface treated with a sulfonating gas to improve certain characteristics (e.g., decrease permeability, stress cracking, swelling) of the polymer.